1. Field of the Invention
The invention relates to a chain stopper for a ball chain, particularly for an operating system of a window blind, such as a horizontal or vertical venetian blind, a roller blind or the like.
2. Description of the Related Art
Ball chain operating systems for window blinds are known in the art, for example, in DE 87 00 548, DE 297 11 893. They generally include a sprocket or drive wheel for driving a driven blind member such as a drive shaft, a ball chain operatively engaging the sprocket wheel, a cover on the sprocket wheel and a chain stopper on the ball chain. In these systems, the sprocket wheel is drivingly connected to a driven member of a blind; in DE 87 00 548, the blind is a roller blind, and in DE 297 11 893, the blind is a vertical venetian blind. A sprocket wheel can also drive other blinds, such as a horizontal venetian blind or a roman shade. The driven member can be a conventional drive shaft of a roller blind, a central control shaft of a roman shade, a lift or tilt shaft of a horizontal venetian blind or a traverse or tilt shaft of a vertical venetian blind, or the like.
The ball chain, in such systems, comprises a plurality of spaced apart balls. The ball chain is looped over the sprocket wheel to operatively engage it, so that first and second depending portions of the ball chain are on either side of the sprocket wheel. By pulling one of the depending portions of the ball chain, the sprocket wheel is rotated in either a clockwise or counter-clockwise direction, and the driven shaft also is rotated. This results in a roller blind being rolled up or unrolled, a venetian blind being tilted or lifted or lowered, a vertical venetian blind being traversed or tilted or a roman shade being lifted or lowered.
The sprocket wheel, in such systems, is provided with a cover. The cover generally is over at least the part of the sprocket wheel where the ball chain is looped over it, but open top covers are also known (e.g., U.S. Pat. No. 2,577,046). The cover is open at the bottom for passage of the opposite depending portions of the ball chain. The cover acts as a guiding means to guide the ball chain into engagement with the sprocket wheel and prevent the ball chain from disengaging from the sprocket wheel.
In such systems, ball chains have been provided with one or more separate members which act as chain stoppers. The stoppers have been adapted to block movement of the ball chains, thus stopping the rotation of the sprocket wheels and operating movement of the blinds. They have also been used to prevent ball chain from being pulled further than necessary for performing desired operating movements of the blinds, for example, for preventing further than a maximum tilt of a venetian blind or preventing a roller blind from being rolled-up too far whereby its bottom bar would bang against its roller or its housing.
The stoppers of DE 87 00 548, DE 297 11 893 grip two adjacent balls of their ball chains and have a cross-section that is bigger than the cross-section of the balls. These stoppers thus block the ball chains at the bottom of their covers and prevent the ball chains from being further pulled over their sprocket wheels. Such stoppers also connect the separate ends of the ball chains by gripping over and connecting together the last ball of each ball chain end.
A drawback of these stoppers is that they are very visible and rather ugly.
Also, their size prevents them from sliding through cord weights, such as are generally used on vertical blinds. Such a cord weight is described, for example, in U.S. Pat. No. 6,325,132, and comprises a pulley rotatably mounted within a weighted outer shell.